Use of a mixture of a complex ester with a monocarboxylic acid to reduce friction

ABSTRACT

The present invention relates to the use of a mixture comprising (I) at least one complex ester obtainable by an esterification reaction between (A) at least one aliphatic linear or branched C 2 -to C 12 -dicarboxylic acid, (B) at least one aliphatic linear or branched polyhydroxy alcohol with 3 to 6 hydroxyl groups, and (C) as a chain stopping agent (C1) at least one aliphatic linear or branched C 1 -to C 30 -monocarboxylic acid in case of an excess of component (B), or (C2) at least one aliphatic linear or branched monobasic C 1 -to C 30 -alcohol in case of an excess of component (A), and (II) at least one aliphatic monocarboxylic acid having from 12 to 30 carbon atoms in a weight ratio of (I):(II) of from 20 to 80:80 to 20 as an additive in a fuel for different purposes.

The present invention relates to the use of a mixture comprising

-   -   (I) at least one complex ester obtainable by an esterification         reaction between     -   (A) at least one aliphatic linear or branched C₂- to         C₁₂-dicarboxylic acid,     -   (B) at least one aliphatic linear or branched polyhydroxy         alcohol with 3 to 6 hydroxyl groups, and     -   (C) as a chain stopping agent         -   (C1) at least one aliphatic linear or branched C₁- to             C₃₀-monocarboxylic acid in case of an excess of component             (B), or         -   (C2) at least one aliphatic linear or branched monobasic C₁-             to C₃₀-alcohol in case of an excess of component (A),     -   and     -   (II) at least one aliphatic monocarboxylic acid having from 12         to 30 carbon atoms     -   in a weight ratio of (I):(II) of from 20 to 80:80 to 20     -   as an additive in a fuel for different purposes.

The present invention further relates to a fuel composition which comprises a gasoline fuel, the mixture of complex ester and aliphatic monocarboxylic acid mentioned and at least one fuel additive with detergent action.

The present invention further relates to an additive concentrate which comprises the mixture of complex ester and aliphatic monocarboxylic acid mentioned and at least one fuel additive with detergent action.

It is known that particular substances in the fuel reduce internal friction in the internal combustion engines, especially in gasoline engines, and thus help to save fuel. Such substances are also referred to as lubricity improvers, friction reducers or friction modifiers. Lubricity improvers customary on the market for gasoline fuels are usually condensation products of naturally occurring carboxylic acids such as fatty acids with polyols such as glycerol or with alkanolamines, for example glyceryl monooleate.

A disadvantage of the prior art lubricity improvers mentioned is poor miscibility with other typically used fuel additives, especially with detergent additives such as polyisobuteneamines and/or carrier oils such as polyalkylene oxides. An important requirement in practice is that the component mixtures or additive concentrates provided are readily pumpable even at relatively low temperatures, especially at outside winter temperatures of, for example, down to −20° C., and remain homogene-ously stable over a prolonged period, i.e. no phase separation and/or precipitates may occur.

Typically, the miscibility problems outlined are avoided by adding relatively large amounts of mixtures of paraffinic or aromatic hydrocarbons with alcohols such as tert-butanol or 2-ethylhexanol as solubilizers to the component mixtures or additive concentrates. In some cases, however, considerable amounts of these expensive solubilizers are necessary in order to achieve the desired homogeneity, and so this solution to the problem becomes uneconomic.

In addition, the prior art lubricity improvers mentioned often have the tendency to form emulsions with water in the component mixtures or additive concentrates or in the fuel itself, such that water which has penetrated can be removed again via a phase separation only with difficulty or at least only very slowly.

WO 99/16849 discloses a complex ester resulting from an esterification reaction between polyfunctional alcohols and polyfunctional carboxylic acids using a chain stopping agent to form ester bonds with the remaining hydroxyl or carboxyl groups, containing as a polyfunctional carboxylic acid component dimerised and/or trimerised fatty acids. This complex ester is recommended for as an additive, a base fluid or a thickener in transmission oils, hydraulic fluids, four-stroke oils, fuel additives, compressor oils, greases, chain oils and for metal working rolling applications.

WO 98/11178 discloses a polyol ester distillate fuel additive synthesized from a polyol and a mono- or polycarboxylic acid in such a manner that the resulting ester has unconverted hydroxyl groups, such polyol ester being useful as a lubricity additive for diesel fuel, jet fuel and kerosene.

WO 03/012015 discloses an additive for improving the lubricity capacity of low-sulphur fuel oils, such additive containing an ester of a bivalent or polyvalent alcohol and a mixture of unsaturated or saturated mono- or dicarboxylic acids whose carbon length are between 8 and 30 carbon atoms.

WO 2015/059063 discloses the use of complex esters to reduce fuel consumption. A lubricity capacity of such complex esters is not described.

It was an object of the present invention to provide fuel additives which firstly increases the lubricating properties of the complex ester additive according to WO 2015/059063 and secondly maintaining its positive effect on effective fuel saving in the operation of a spark-ignited internal combustion engine while remaining homogeneously stable over a prolonged period without any phase separation and/or precipitates.

Accordingly, the use of a mixture of complex ester and aliphatic monocarboxylic acid as described above as an additive in a fuel for improving the lubricating properties in the operation of an internal combustion engine with this fuel has been found. Preferably, the said use as an additive in a gasoline fuel for improving the lubricating properties and simultaneously reducing fuel consumption in the operation of a spark-ignited internal combustion engine with this fuel or as an additive in a gasoline fuel for improving the lubricating properties and simultaneously reduction of fuel consumption in the operation of a self-ignition internal combustion engine with this fuel has been found.

It can be assumed that the cause of the fuel saving by virtue of the mixture of complex ester and aliphatic monocarboxylic acid mentioned is based substantially on the effect thereof as an additive which reduces internal friction in the internal combustion engines, especially in gasoline engines. The mixture mentioned thus functions in the context of the present invention essentially as a lubricity improver.

Furthermore, the use of a mixture of complex ester and aliphatic monocarboxylic acid as described above as an additive in a fuel for reduction of the friction in internal combustion engines and for improving acceleration of internal combustion engines has been found.

Furthermore, the use of a mixture of complex ester and aliphatic monocarboxylic acid as described above as an additive in a fuel for improving the lubricity of lubricant oils contained in an internal combustion engine for lubricating purposes by operating the internal combustion engine with a fuel containing an effective amount of at least one of the said mixture of complex ester and aliphatic monocarboxylic acid has been found.

It can be assumed that a part of the mixture mentioned contained in the fuel is transported via the combustion chamber where the additive containing fuel is burnt into the lubricant oils and acting there as a further lubricating agent. The advantage of this mechanism is that the said further lubricating agent is continuously refreshed by the fuel feeding.

Spark-ignition internal combustion engines are preferably understood to mean gasoline engines, which are typically ignited with spark plugs. In addition to the customary four- and two-stroke gasoline engines, spark-ignition internal combustion engines also include other engine types, for example the Wankel engine. These are generally engines which are operated with conventional gasoline types, especially gasoline types according to EN 228, gasoline-alcohol mixtures such as Flex fuel with 75 to 85% by volume of ethanol, liquid pressure gas (“LPG”) or compressed natural gas (“CNG”) as fuel.

However, the inventive use of the complex ester mentioned also relates to newly developed internal combustion engines such as the “HCCl” engine, which is self-igniting and is operated with gasoline fuel.

The instant invention works preferably with direct injection gasoline driven combustion engines.

Compound (I) of the mixture according to the present invention is a complex ester obtainable by an esterification reaction.

The aliphatic dicarboxylic acids of component (A) may be branched or preferably linear; they may be unsaturated or preferably saturated. Typical examples for component (A) are ethanedioic acid (oxalic acid), propanedioic acid (malonic acid), butanedioic acid (succinic acid), (Z)-butenedioic acid (maleic acid), (E)-butenedioic acid (fumaric acid), pentanedioic acid (glutaric acid), pent-2-enedioic acid (glutaconic acid), hexanedioic acid (adipic acid), heptanedioic acid (pimelic acid), octanedioic acid (suberic acid), nonanedioic acid (azelaic acid), decanedioic acid (sebacic acid), undecanedioic acid, dodecanedioic acid, dodec-2-enedioic acid (traumatic acid) and (2E,4E)-hexa-2,4-dienedioic acid (muconic acid). Mixture of the above aliphatic dicarboxylic acids can also be used.

In a preferred embodiment, the at least one aliphatic dicarboxylic acid of component (A) is selected from aliphatic linear C₆- to C₁₀-dicarboxylic acids which are preferably saturated. Most preferred are adipic acid and sebacic acid.

The aliphatic polyhydroxy alcohols of component (B) may be branched or linear; they may be unsaturated or preferably saturated; they may contain of from 3 to 12, preferably of from 3 to 8, especially of from 3 to 6 carbon atoms and preferably 3, 4 or 5 hydroxyl groups. Typical examples for component (B) are trimethylolethane, trimethylolpropane, trimethylolbutane, sorbitol, glycerin and pentaerythritol. Mixtures of the above aliphatic polyhydroxy alcohols can also be used.

In a preferred embodiment, the at least one aliphatic polyhydroxy alcohol of component (B) is selected from glycerin, trimethylolpropane and pentaerythritol.

Depending whether component (B) is used for the esterification reaction in an excess compared with component (A), resulting in remaining free hydroxyl groups, or component (A) is used for the esterification reaction in an excess compared with component (B), resulting in remaining free carboxylic groups, chain stopping agent (C1) or (C2) is used for the synthesis of the complex ester mentioned. Carboxylic ester component (C1) will transform remaining free hydroxyl groups into additional carboxylic ester groups. Monobasic alcohol component (C2) will transform remaining free carboxylic groups into additional carboxylic ester groups.

The aliphatic monocarboxylic acids of component (C1) may be branched or linear; they may be unsaturated or preferably saturated. Typical examples for component (A) are formic acid, acetic acid, propionic acid, 2,2-dimethyl propionic acid (neopentanoic acid), hexanoic acid, octanoic acid (caprylic acid), 2-ethylhexanoic acid, 3,5,5-trimethyl hexanoic acid, nonanoic acid, decanoic acid (capric acid), undecanoic acid, dodecanoic acid (lauric acid), tridecanoic acid, tetradecanoic acid (myristic acid), hexadecanoic acid (palmitic acid), octadecanoic acid (stearic acid), isostearic acid, oleic acid, linoleic acid, linolaidic acid, erucic acid, arachidic acid, behenic acid, lignoceric acid and cerotic acid. The above monocarboxylic acids, including the so called fatty acids, may be of synthetic or of natural origin. Mixtures of the above aliphatic monocarboxylic acids can also be used.

In a preferred embodiment, the at least one aliphatic monocarboxylic acid of component (C1) is selected from aliphatic linear or branched C₈- to C₁₈-monocarboxylic acids.

The aliphatic monobasic alcohols of component (C2) may be branched or linear; they may be unsaturated or preferably saturated. Typical examples for component (C2) are methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, sec-butanol, tert-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, 2-ethylhexanol, n-nonanol, 2-propylheptanol, n-decanol, n-undecanol, n-dodecanol, n-tridecanol, iso-tridecanol, n-tetradecanol, iso-tetradecanol, n-hexadecanol, n-octadecanol, iso-octadecanol and n-eicosanol. Mixtures of the above monobasic alcohols can also be used. The said monobasic alcohols may have been alkoxylated by means of hydrocarbyl epoxides like ethylene oxide, propylene oxide and/or butylene oxide resulting in monocapped polyethers before being used as chain stopping agents for preparing the complex esters mentioned.

In a preferred embodiment, the at least one aliphatic monobasic alcohol of component (C2) is selected from linear or branched C₈- to C₁₈-alkanols.

The synthesis of the complex ester mentioned is in principle known in the art. In more detail, it can be prepared by mixing and reacting component (A) with (B) and subsequently reacting the intermediate ester formed by (A) and (B) with component (C). As an alternative, it can also be prepared by mixing and reacting components (A), (B) and (C) simultaneously.

The complex ester mentioned is normally composed of at least 2 molecule units of component (A), at least 3 molecule units of component (B) and the corresponding number of molecule units of chain stopping agent (C), or of at least 2 molecule units of component (B), at least 3 molecule units of component (A) and the corresponding number of molecule units of chain stopping agent (C).

In a preferred embodiment, the complex ester mentioned is composed of from 2 to 9 molecule units, especially of from 2 to 5 molecule units of component (A) and of from 3 to 10 molecule units, especially of from 3 to 6 molecule units of component (B), component (B) being in excess compared with component (A), with remaining free hydroxyl groups of (B) being completely or partly capped with a corresponding number of molecule units of component (C1).

In another preferred embodiment, the complex ester mentioned is composed of from 3 to 10 molecule units, especially of from 3 to 6 molecule units of component (A) and of from 2 to 9 molecule units, especially of from 2 to 5 molecule units of component (B), component (A) being in excess compared with component (B), with remaining free carboxyl groups of (A) being completely or partly capped with a corresponding number of molecule units of component (C2).

A typical complex ester useful for the instant invention is composed of 3 or 4 molecule units of component (A), especially of at least one aliphatic linear C₆- to C₁₀-dicarboxylic acid such as adipic acid and/or sebacic acid, of 4 or 5 molecule units of component (B), especially of glycerin, trimethylolpropane and/or pentaerythritol, and of 6 to 12 molecule units of component (C1), especially of at least one aliphatic linear or branched C₈- to C₁₈-monocarboxylic acid such as octanoic acid, 2-ethylhexanoic acid, 3,5,5-trimethyl hexanoic acid, nonanoic acid, decanoic acid and/or isostearic acid.

The complex ester mentioned is oil soluble, which means that, when mixed with mineral oils and/or fuels in a weight ratio of 10:90, 50:50 and 90:10, the complex ester does not show phase separation after standing for 24 hours at room temperature for at least two weight ratios out of the three weight ratios 10:90, 50:50 and 90:10.

Compound (II) of the mixture according to the present invention is at least one aliphatic monocarboxylic acid having from 12 to 30 carbon atoms, preferably having from 14 to 26 carbon atoms, very preferably having from 16 to 24 carbon atoms, and especially having from 18 to 20 carbon atoms.

The monocarboxylic acid can be saturated or onefold, twofold or multifold unsaturated, preferably unsaturated, very preferably onefold unsaturated.

It is also possible to us a mixture of aliphatic monocarboxylic acids, especially from natural and renewable sources, e.g. animal or preferably vegetable oil. Such mixtures of aliphatic monocarboxylic acids are usually obtained by saponification of natural oils and yield mixtures of aliphatic monocarboxylic acids with different number of carbon atoms depending on the source and origin of the natural oil. Preferred are linseed oil, coconut fat, palm kernel oil, palm oil, soy bean oil, peanut oil, cocoa butter, shea butter, cotton seed oil, corn oil, sunflower oil, rapeseed oil or castor oil.

Examples for aliphatic monocarboxylic acids are dodecanoic acid (lauric acid), tridecanoic acid, tetradecanoic acid (myristic acid), hexadecanoic acid (palmitic acid), octadecanoic acid (stearic acid), isostearic acid, oleic acid, linoleic acid, linolaidic acid, erucic acid, arachidic acid, behenic acid, lignoceric acid and cerotic acid, preferred are tetradecanoic acid (myristic acid), hexadecanoic acid (palmitic acid), octadecanoic acid (stearic acid), isostearic acid, oleic acid, linoleic acid, linolaidic acid, erucic acid, arachidic acid, and behenic acid, very preferred are hexadecanoic acid (palmitic acid), octadecanoic acid (stearic acid), isostearic acid, oleic acid, linoleic acid, and linolaidic acid, and especially oleic acid, linoleic acid, and linolaidic acid. Oleic acid is especially preferred.

In a preferred embodiment the monocarboxylic acid (II) is different from the C₁- to C₃₀-monocarboxylic acid (C1) used in the production of compound the complex ester (I).

The mixtures according to the present invention comprise compounds (I) and (II) in a weight ratio of from 20 to 80:from 80 to 20, preferably in a weight ratio of from 25 to 75:from 75 to 25, more preferably in a weight ratio of from 30 to 70:from 70 to 30, and very preferably in a weight ratio of from 35 to 65:from 65 to 35.

The mixture may comprise further components, preferably solvents or corrosion inhibitors.

In a preferred embodiment the mixtures according to the present invention consist of compounds (I) and (II) only so that the above-mentioned weight ratios add up to 100% by weight.

The present invention also provides a fuel composition which comprises, in a major amount, a gasoline fuel and, in a minor amount, at least one mixture of at least one complex ester and at least one carboxylic acid mentioned, and at least one fuel additive (D) which is different from the said complex esters (I) and said carboxylic acid (II) and has detergent action.

Typically, the amount of the mixture is added to the fuel so that the amount of the at least one complex ester in the gasoline fuel is 10 to 5000 ppm by weight, more preferably 20 to 2000 ppm by weight, even more preferably 30 to 1000 ppm by weight and especially 40 to 500 ppm by weight, for example 50 to 300 ppm by weight and the amount of the carboxylic acid in the fuel is 10 to 100 ppm by weight, preferably 12 to 80 ppm by weight, more preferably 15 to 70 ppm by weight, very preferably 20 to 50 ppm by weight and especially 25 to 35 ppm by weight.

Useful gasoline fuels include all conventional gasoline fuel compositions. A typical representative which shall be mentioned here is the Eurosuper base fuel to EN 228, which is customary on the market. In addition, gasoline fuel compositions of the specification according to WO 00/47698 are also possible fields of use for the present invention. In addition, in the context of the present invention, gasoline fuels shall also be understood to mean alcohol-containing gasoline fuels, especially ethanol-containing gasoline fuels, as described, for example, in WO 2004/090079, for example Flex fuel with an ethanol content of 75 to 85% by volume, or gasoline fuel comprising 85% by volume of ethanol (“E85”), but also the “E100” fuel type, which is typically azeotropically distilled ethanol and thus consists of approx. 96% by volume of C₂H₅OH and approx. 4% by volume of water (H₂O).

The mixture of complex ester and carboxylic acid mentioned may be added to the particular base fuel either alone or in the form of fuel additive packages (for gasoline fuels also called “gasoline performance packages”). Such packages are fuel additive concentrates and generally also comprise, as well as solvents, and as well as the at least one fuel additive which is different from the said complex esters or carboxylic acid and has detergent action, a series of further components as coadditives, which are especially carrier oils, corrosion inhibitors, demulsifiers, dehazers, antifoams, combustion improvers, antioxidants or stabilizers, antistats, metallocenes, metal deactivators, solubilizers, markers and/or dyes.

Detergents or detergent additives as the at least one fuel additive which is different from the said complex esters and carboxylic acids (II) and has detergent action, referred to hereinafter as component (D), typically refer to deposition inhibitors for fuels. The detergent additives are preferably amphiphilic substances which possess at least one hydrophobic hydrocarbyl radical having a number-average molecular weight (Mn) of 85 to 20 000, especially of 300 to 5000, in particular of 500 to 2500, and at least one polar moiety.

The inventive fuel composition comprises, as the at least one fuel additive (D) which is different from the said complex esters and has detergent action, at least one representative which is selected from compounds bearing at least one:

-   -   (Da) mono- or polyamino group having up to 6 nitrogen atoms, at         least one nitrogen atom having basic properties;     -   (Db) nitro group, optionally in combination with at least one         hydroxyl group;     -   (Dc) hydroxyl group in combination with at least one mono- or         polyamino group, at least one nitrogen atom having basic         properties;     -   (Dd) carboxyl group or their alkali metal or alkaline earth         metal salts;     -   (De) sulfonic acid group or their alkali metal or alkaline earth         metal salts;     -   (Df) polyoxy-C₂-C₄-alkylene moiety terminated by at least one         hydroxyl group, mono- or polyamino group, at least one nitrogen         atom having basic properties, or by at least one carbamate         group;     -   (Dg) carboxylic ester group;     -   (Dh) moieties derived from succinic anhydride and having at         least one hydroxyl and/or amino and/or amido and/or imido group;         and/or     -   (Di) moiety obtained by Mannich reaction of substituted phenols         with aldehydes and mono- or polyamines.

The hydrophobic hydrocarbon radical in the above detergent additives, which ensures the adequate solubility in the fuel composition, has a number-average molecular weight (Mn) of 85 to 20 000, especially of 300 to 5000, in particular of 500 to 2500. Useful typical hydrophobic hydrocarbyl radicals, especially in conjunction with the polar moieties (Da), (Dc), (Dh) and (Di), are relatively long-chain alkyl or alkenyl groups, especially the polypropenyl, polybutenyl and polyisobutenyl radicals each having M_(n)=300 to 5000, especially 500 to 2500, in particular 700 to 2300.

Examples of the above groups of detergent additives include the following:

Additives comprising mono- or polyamino groups (Da) are preferably polyalkenemono- or polyalkenepolyamines based on polypropene or on highly-reactive (i.e. having predominantly terminal double bonds in the α- and/or β-position such as vinylidene double bonds) or conventional (i.e. having predominantly internal double bonds) polybutene or polyisobutene having M_(n)=300 to 5000. Such detergent additives based on highly-reactive polybutene or polyisobutene, which are normally prepared by hydroformylation of the poly(iso)butene and subsequent reductive amination with ammonia, monoamines or polyamines, are known from EP-A 244 616. When the preparation of the additives proceeds from polybutene or polyisobutene having predominantly internal double bonds (usually in the β- and/or γ-positions), one possible preparative route is by chlorination and subsequent amination or by oxidation of the double bond with air or ozone to give the carbonyl or carboxyl compound and subsequent amination under reductive (hydrogenating) conditions. The amines used here for the amination may be, for example, ammonia, monoamines or polyamines such as dimethylaminopropylamine, ethylenediamine, diethylenetriamine, triethylenetetramine or tetraethylenepentamine. Corresponding additives based on polypropene are described in particular in WO-A-94/24231.

Further preferred additives comprising monoamino groups (Da) are the hydrogenation products of the reaction products of polyisobutenes having an average degree of polymerization P=5 to 100 with nitrogen oxides or mixtures of nitrogen oxides and oxygen, as described in particular in WO-A-97/03946.

Further preferred additives comprising monoamino groups (Da) are the compounds obtainable from polyisobutene epoxides by reaction with amines and subsequent dehydration and reduction of the amino alcohols, as described in particular in DE-A-196 20 262.

Additives comprising nitro groups (Db), optionally in combination with hydroxyl groups, are preferably reaction products of polyisobutenes having an average degree of polymerization P=5 to 100 or 10 to 100 with nitrogen oxides or mixtures of nitrogen oxides and oxygen, as described in particular in WO-A-96/03367 and in WO-A 96/03479. These reaction products are generally mixtures of pure nitropolyisobutenes (e.g. α,β-dinitropolyisobutene) and mixed hydroxynitropolyisobutenes (e.g. α-nitro-β-hydroxypolyisobutene).

Additives comprising hydroxyl groups in combination with mono- or polyamino groups (Dc) are in particular reaction products of polyisobutene epoxides obtainable from polyisobutene having preferably predominantly terminal double bonds and M_(n)=300 to 5000, with ammonia or mono- or polyamines, as described in particular in EP-A-476 485.

Additives comprising carboxyl groups or their alkali metal or alkaline earth metal salts (Dd) are preferably copolymers of C₂-C₄₀-olefins with maleic anhydride which have a total molar mass of 500 to 20 000 and some or all of whose carboxyl groups have been converted to the alkali metal or alkaline earth metal salts and any remainder of the carboxyl groups has been reacted with alcohols or amines. Such additives are disclosed in particular by EP-A-307 815. Such additives serve mainly to prevent valve seat wear and can, as described in WO-A-87/01126, advantageously be used in combination with customary fuel detergents such as poly(iso)buteneamines or polyetheramines.

Additives comprising sulfo groups or their alkali metal or alkaline earth metal salts (De) are preferably alkali metal or alkaline earth metal salts of an alkyl sulfosuccinate, as described in particular in EP-A-639 632. Such additives serve mainly to prevent valve seat wear and can be used advantageously in combination with customary fuel detergents such as poly(iso)buteneamines or polyetheramines.

Additives comprising polyoxy-C₂-C₄-alkylene moieties (Df) are preferably polyethers or polyetheramines which are obtainable by reaction of C₂-C₆₀-alkanols, C₆-C₃₀-alkane-diols, mono- or di-C₂-C₃₀-alkylamines, C₁-C₃₀-alkylcyclohexanols or C₁-C₃₀-alkylphenols with 1 to 30 mol of ethylene oxide and/or propylene oxide and/or butylene oxide per hydroxyl group or amino group and, in the case of the polyetheramines, by subsequent reductive amination with ammonia, monoamines or polyamines. Such products are described in particular in EP-A-310 875, EP-A-356 725, EP-A-700 985 and U.S. Pat. No. 4,877,416. In the case of polyethers, such products also have carrier oil properties. Typical examples of these are tridecanol butoxylates, isotridecanol butoxylates, isononyl-phenol butoxylates and polyisobutenol butoxylates and propoxylates and also the corresponding reaction products with ammonia.

Additives comprising carboxylic ester groups (Dg) are preferably esters of mono-, di- or tricarboxylic acids with long-chain alkanols or polyols, in particular those having a minimum viscosity of 2 mm²/s at 100° C., as described in particular in DE-A-38 38 918. The mono-, di- or tricarboxylic acids used may be aliphatic or aromatic acids, and particularly suitable ester alcohols or ester polyols are long-chain representatives having, for example, 6 to 24 carbon atoms. Typical representatives of the esters are adipates, phthalates, isophthalates, terephthalates and trimellitates of isooctanol, of isononanol, of isodecanol and of isotridecanol. Such products also have carrier oil properties.

Additives comprising moieties derived from succinic anhydride and having hydroxyl and/or amino and/or amido and/or imido groups (Dh) are preferably corresponding derivatives of alkyl- or alkenyl-substituted succinic anhydride and especially the corresponding derivatives of polyisobutenylsuccinic anhydride which are obtainable by reacting conventional or high-reactivity polyisobutene having M_(n)=300 to 5000 with maleic anhydride by a thermal route or via the chlorinated polyisobutene. Of particular interest in this context are derivatives with aliphatic polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine or tetraethylenepentamine. The moieties having hydroxyl and/or amino and/or amido and/or imido groups are, for example, carboxylic acid groups, acid amides of monoamines, acid amides of di- or polyamines which, in addition to the amide function, also have free amine groups, succinic acid derivatives having an acid and an amide function, carboximides with monoamines, carboximides with di- or polyamines which, in addition to the imide function, also have free amine groups, or diimides which are formed by the reaction of di- or polyamines with two succinic acid derivatives. Such fuel additives are described especially in U.S. Pat. No. 4,849,572.

The detergent additives from group (Dh) are preferably the reaction products of alkyl- or alkenyl-substituted succinic anhydrides, especially of polyisobutenylsuccinic anhydrides (“PIBSAs”), with amines and/or alcohols. These are thus derivatives which are derived from alkyl-, alkenyl- or polyisobutenylsuccinic anhydride and have amino and/or amido and/or imido and/or hydroxyl groups. It is self-evident that these reaction products are obtainable not only when substituted succinic anhydride is used, but also when substituted succinic acid or suitable acid derivatives, such as succinyl halides or succinic esters, are used.

The additized fuel may comprise at least one detergent based on a polyisobutenyl-substituted succinimide. Especially of interest are the imides with aliphatic polyamines. Particularly preferred polyamines are ethylenediamine, diethylenetriamine, triethylenetetramine, pentaethylenehexamine and in particular tetraethylenepentamine. The polyisobutenyl radical has a number-average molecular weight M_(n) of preferably from 500 to 5000, more preferably from 500 to 2000 and in particular of about 1000.

Additives comprising moieties (Di) obtained by Mannich reaction of substituted phenols with aldehydes and mono- or polyamines are preferably reaction products of polyisobutene-substituted phenols with formaldehyde and mono- or polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine or dimethylaminopropylamine. The polyisobutenyl-substituted phenols may originate from conventional or high-reactivity polyisobutene having M_(n)=300 to 5000. Such “polyisobutene Mannich bases” are described especially in EP-A-831 141.

The inventive fuel composition comprises the at least one fuel additive which is different from the complex ester mentioned and has detergent action, and is normally selected from the above groups (Da) to (Di), in an amount of typically 10 to 5000 ppm by weight, more preferably of 20 to 2000 ppm by weight, even more preferably of 30 to 1000 ppm by weight and especially of 40 to 500 ppm by weight, for example of 50 to 250 ppm by weight.

The detergent additives (D) mentioned are preferably used in combination with at least one carrier oil. In a preferred embodiment, the inventive fuel composition comprises, in addition to the at least one inventive reaction product and the at least one fuel additive which is different than the inventive reaction product and has detergent action, as a further fuel additive in a minor amount, at least one carrier oil.

Suitable mineral carrier oils are the fractions obtained in crude oil processing, such as brightstock or base oils having viscosities, for example, from the SN 500-2000 class; but also aromatic hydrocarbons, paraffinic hydrocarbons and alkoxyalkanols. Likewise useful is a fraction which is obtained in the refining of mineral oil and is known as “hydrocrack oil” (vacuum distillate cut having a boiling range of from about 360 to 500° C., obtainable from natural mineral oil which has been catalytically hydrogenated under high pressure and isomerized and also deparaffinized). Likewise suitable are mixtures of abovementioned mineral carrier oils.

Examples of suitable synthetic carrier oils are selected from: polyolefins (poly-alpha-olefins or poly(internal olefins)), (poly)esters, (poly)alkoxylates, polyethers, aliphatic polyetheramines, alkylphenol-started polyethers, alkylphenol-started polyetheramines and carboxylic esters of long-chain alkanols.

Examples of suitable polyolefins are olefin polymers having M_(n)=from 400 to 1800, in particular based on polybutene or polyisobutene (hydrogenated or unhydrogenated).

Examples of suitable polyethers or polyetheramines are preferably compounds comprising polyoxy-C₂-C₄-alkylene moieties which are obtainable by reacting C₂-C₆₀-alkanols, C₆-C₃₀-alkanediols, mono- or di-C₂-C₃₀-alkylamines, C₁-C₃₀-alkylcyclohexanols or C₁-C₃₀-alkylphenols with from 1 to 30 mol of ethylene oxide and/or propylene oxide and/or butylene oxide per hydroxyl group or amino group, and, in the case of the polyetheramines, by subsequent reductive amination with ammonia, monoamines or polyamines. Such products are described in particular in EP-A-310 875, EP-A-356 725, EP-A-700 985 and U.S. Pat. No. 4,877,416. For example, the polyether-amines used may be poly-C₂-C₆-alkylene oxide amines or functional derivatives thereof. Typical examples thereof are tridecanol butoxylates or isotridecanol butoxylates, isononylphenol butoxylates and also polyisobutenol butoxylates and propoxylates, and also the corresponding reaction products with ammonia.

Examples of carboxylic esters of long-chain alkanols are in particular esters of mono-, di- or tricarboxylic acids with long-chain alkanols or polyols, as described in particular in DE-A-38 38 918. The mono-, di- or tricarboxylic acids used may be aliphatic or aromatic acids; suitable ester alcohols or polyols are in particular long-chain representatives having, for example, from 6 to 24 carbon atoms. Typical representatives of the esters are adipates, phthalates, isophthalates, terephthalates and trimellitates of isooctanol, isononanol, isodecanol and isotridecanol, for example di(n- or isotridecyl) phthalate.

Further suitable carrier oil systems are described, for example, in DE-A-38 26 608, DE-A-41 42 241, DE-A-43 09 074, EP-A-0 452 328 and EP-A-0 548 617.

Examples of particularly suitable synthetic carrier oils are alcohol-started polyethers having from about 5 to 35, for example from about 5 to 30, C₃-C₆-alkylene oxide units, for example selected from propylene oxide, n-butylene oxide and isobutylene oxide units, or mixtures thereof. Nonlimiting examples of suitable starter alcohols are long-chain alkanols or phenols substituted by long-chain alkyl in which the long-chain alkyl radical is in particular a straight-chain or branched C₆-C₁₈-alkyl radical. Preferred examples include tridecanol and nonylphenol.

Further suitable synthetic carrier oils are alkoxylated alkylphenols, as described in DE-A-101 02 913.

Preferred carrier oils are synthetic carrier oils, particular preference being given to polyethers.

When a carrier oil is used in addition, it is added to the inventive additized fuel in an amount of preferably from 1 to 1000 ppm by weight, more preferably from 10 to 500 ppm by weight and in particular from 20 to 100 ppm by weight.

In a preferred embodiment, the inventive fuel composition comprises, in addition to the at least one inventive reaction product, the at least one fuel additive which is different from the complex ester mentioned and has detergent action, and optionally the at least one carrier oil, as a further fuel additive in a minor amount at least one tertiary hydrocarbyl amine of formula NR¹R²R³ wherein R¹, R² and R³ are the same or different C₁- to C₂₀-hydrocarbyl residues with the proviso that the overall number of carbon atoms in formula NR¹R²R³ does not exceed 30.

Tertiary hydrocarbyl amines have proven to be advantageous with regard to use as performance additives in fuels controlling deposits. Besides their superior performance behavior, they are also good to handle as their melting points are normally low enough to be usually liquid at ambient temperature.

“Hydrocarbyl residue” for R¹ to R³ shall mean a residue which is essentially composed of carbon and hydrogen, however, it can contain in small amounts heteroatomes, especially oxygen and/or nitrogen, and/or functional groups, e.g. hydroxyl groups and/or carboxylic groups, to an extent which does not distort the predominantly hydrocarbon character of the residue. Hydrocarbyl residues are preferably alkyl, alkenyl, alkinyl, cycloalkyl, aryl, alkylaryl or arylalkyl groups. Especially preferred hydrocarbyl residues for R¹ to R³ are linear or branched alkyl or alkenyl groups.

The overall number of carbon atoms in the tertiary hydrocarbyl amine mentioned is at most 30, preferably at most 27, more preferably at most 24, most preferably at most 20. Preferably, the minimum overall number of carbon atoms in formula NR¹R²R³ is 6, more preferably 8, most preferably 10. Such size of the tertiary hydrocarbyl amine mentioned corresponds to molecular weight of about 100 to about 450 for the largest range and of about 150 to about 300 for the smallest range; most usually, tertiary hydrocarbyl amines mentioned within a molecular range of from 100 to 300 are used.

The three C₁- to C₂₀-hydrocarbyl residues may be identical or different. Preferably, they are different, thus creating an amine molecular which exhibits an oleophobic moiety (i.e. the more polar amino group) and an oleophilic moiety (i.e. a hydrocarbyl residue with a longer chain length or a larger volume). Such amine molecules with oleophobic/oleophilic balance have proved to show the best deposit control performance according the present invention.

Preferably, a tertiary hydrocarbyl amine of formula NR¹R²R³ is used wherein at least two of hydrocarbyl residues R¹, R² and R³ are different with the proviso that the hydrocarbyl residue with the most carbon atoms differ in carbon atom number from the hydrocarbyl residue with the second most carbon atoms in at least 3, preferably in at least 4, more preferably in at least 6, most preferably in at least 8. Thus, the tertiary amines mentioned exhibit hydrocarbyl residues of two or three different chain length or different volume, respectively.

Still more preferably, a tertiary hydrocarbyl amine of formula NR¹R²R³ is used wherein one or two of R¹ to R³ are C₇- to C₂₀-hydrocarbyl residues and the remaining two or one of R¹ to R³ are C₁- to C₄-hydrocarbyl residues.

The one or the two longer hydrocarbyl residues, which may be in case of two residues identical or different, exhibit from 7 to 20, preferably from 8 to 18, more preferably from 9 to 16, most preferably from 10 to 14 carbon atoms. The one or the two remaining shorter hydrocarbyl residues, which may be in case of two residues identical or different, exhibit from 1 to 4, preferably from 1 to 3, more preferably 1 or 2, most preferably 1 carbon atom(s). Besides the desired deposit controlling performance, the oleophilic long-chain hydrocarbyl residues provide further advantageous properties to the tertiary amines, i.e. high solubility for gasoline fuels and low volatility.

More preferably, tertiary hydrocarbyl amines of formula NR¹R²R³ are used, wherein R¹ is a C₈- to C₁₈-hydrocarbyl residue and R² and R³ are independently of each other C₁- to C₄-alkyl radicals. Still more preferably, tertiary hydrocarbyl amines of formula NR¹R²R³ are used, wherein R¹ is a C₉- to C₁₆-hydrocarbyl residue and R² and R³ are both methyl radicals.

Examples for suitable linear or branched C₁- to C₂₀-alkyl residues for R¹ to R³ are: methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec.-butyl, tert-butyl, n-pentyl, tert-pentyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl,1,2-dimethylpropyl, n-hexyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2-ethylbutyl, n-heptyl, 1-methylhexyl, 2-methylhexyl, 3-methylhexyl, 4-methylhexyl, 5-methylhexyl, 1,1-dimethylpentyl, 1,2-dimethylpentyl, 2,2-dimethylpentyl, 2,3-dimethylpentyl, 2,4-dimethylpentyl, 2,5-dimethylpentyl, 2-diethylpentyl, 3-diethyl-pentyl, n-octyl, 1-methylheptyl, 2-methylheptyl, 3-methylheptyl, 4-methylheptyl, 5-methylheptyl, 6-methylheptyl, 1,1-dimethylhexyl, 1,2-dimethylhexyl, 2,2-dimethylhexyl, 2,3-dimethylhexyl, 2,4-dimethylhexyl, 2,5-dimethylhexyl, 2,6-dimethylhexyl, 2-ethylhexyl, 3-ethylhexyl, 4-ethylhexyl, n-nonyl, iso-nonyl, n-decyl, 1-propylheptyl, 2-propyl-heptyl, 3-propylheptyl, n-undecyl, n-dodecyl, n-tridecyl, iso-tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl and eicosyl.

Examples for suitable linear or branched C₂- to C₂₀-alkenyl and -alkinyl residues for R¹ to R³ are: vinyl, allyl, oleyl and propin-2-yl.

Tertiary hydrocarbyl amines of formula NR¹R²R³ with long-chain alkyl and alkenyl residues can also preferably be obtained or derived from natural sources, i.e. from plant or animal oils and lards. The fatty amines derived from such sources which are suitable as such tertiary hydrocarbyl amines normally form mixtures of differents similar species such as homologues, e.g. tallow amines containing as main components tetradecyl amine, hexadecyl amine, octadecyl amine and octadecenyl amine (oleyl amine). Further examples of suitable fatty amines are: coco amines and palm amines. Unsaturated fatty amines which contain alkenyl residues can be hydrogenated and used in this saturated form.

Examples for suitable C₃- to C₂₀-cycloalkyl residues for R¹ to R³ are: cyclopropyl, cyclobutyl, 2-methylcyclohexyl, 3-methylcyclohexyl, 4-methylcyclohexyl, 2,3-dimethyl-cyclohexyl, 2,4-dimethylcyclohexyl, 2,5-dimethylcyclohexyl, 2,6-dimethylcyclohexyl, 3,4-dimethylcyclohexyl, 3,5-dimethylcyclohexyl, 2-ethylcyclohexyl, 3-ethylcyclohexyl, 4-ethylcyclohexyl, cyclooctyl and cyclodecyl.

Examples for suitable C₇- to C₂₀-aryl, -alkylaryl or -arylalkyl residues for R¹ to R³ are: naphthyl, tolyl, xylyl, n-octylphenyl, n-nonylphenyl, n-decylphenyl, benzyl, 1-phenyl-ethyl, 2-phenylethyl, 3-phenylpropyl and 4-butylphenyl.

Typical examples for suitable tertiary hydrocarbyl amines of formula NR¹R²R³ are the following:

N,N-dimethyl-n-butylamine, N,N-dimethyl-n-pentylamine, N,N-dimethyl-n-hexylamine, N,N-dimethyl-n-heptylamine, N,N-dimethyl-n-octylamine, N,N-dimethyl-2-ethylhexyl-amine, N,N-di-methyl-n-nonylamine, N,N-dimethyl-iso-nonylamine, N,N-dimethyl-n-decylamine, N,N-dimethyl-2-propylheptylamine, N,N-dimethyl-n-undecylamine, N,N-dimethyl-n-dodecylamine, N,N-dimethyl-n-tridecylamine, N,N-dimethyl-iso-tridecyl-amine, N,N-dimethyl-n-tetradecylamine, N,N-dimethyl-n-hexadecylamine, N,N-di-methyl-n-octadecylamine, N,N-dimethyl-eicosylamine, N,N-dimethyl-oleylamine;

N,N-diethyl-n-heptylamine, N,N-diethyl-n-octylamine, N,N-diethyl-2-ethylhexylamine, N,N-diethyl-n-nonylamine, N,N-diethyl-iso-nonylamine, N,N-diethyl-n-decylamine, N,N-diethyl-2-propylheptylamine, N,N-diethyl-n-undecylamine, N,N-diethyl-n-dodecylamine, N,N-diethyl-n-tridecylamine, N,N-diethyl-iso-tridecylamine, N,N-diethyl-n-tetradecyl-amine, N,N-diethyl-n-hexadecylamine, N,N-di-ethyl-n-octadecylamine, N,N-diethyl-eicosylamine, N,N-diethyl-oleylamine;

N,N-di-(n-propyl)-n-heptylamine, N,N-di-(n-propyl)-n-octylamine, N,N-di-(n-propyl)-2-ethylhexylamine, N,N-di-(n-propyl)-n-nonylamine, N,N-di-(n-propyl)-iso-nonylamine, N,N-di-(n-propyl)-n-decylamine, N,N-di-(n-propyl)-2-propylheptylamine, N,N-di-(n-propyl)-n-undecylamine, N,N-di-(n-propyl)-n-dodecylamine, N,N-di-(n-propyl)-n-tri-decylamine, N,N-di-(n-propyl)-iso-tridecylamine, N,N-di-(n-propyl)-n-tetradecylamine, N,N-di-(n-propyl)-n-hexadecylamine, N,N-di-(n-propyl)-n-octadecylamine, N,N-di-(n-propyl)-eicosylamine, N,N-di-(n-propyl)-oleylamine;

N,N-di-(n-butyl)-n-heptylamine, N,N-di-(n-butyl)-n-octylamine, N,N-di-(n-butyl)-2-ethyl-hexylamine, N,N-di-(n-butyl)-n-nonylamine, N,N-di-(n-butyl)-iso-nonylamine, N,N-di-(n-butyl)-n-decylamine, N,N-di-(n-butyl)-2-propylheptylamine, N,N-di-(n-butyl)-n-undecyl-amine, N,N-di-(n-butyl)-n-dodecylamine, N,N-di-(n-butyl)-n-tridecylamine, N,N-di-(n-butyl)-iso-tridecylamine, N,N-di-(n-butyl)-n-tetradecylamine, N,N-di-(n-butyl)-n-hexa-decylamine, N,N-di-(n-butyl)-n-octadecylamine, N,N-di-(n-butyl)-eicosylamine, N,N-di-(n-butyl)-oleylamine;

N-methyl-N-ethyl-n-heptylamine, N-methyl-N-ethyl-n-octylamine, N-methyl-N-ethyl-2-ethylhexylamine, N-methyl-N-ethyl-n-nonylamine, N-methyl-N-ethyl-iso-nonylamine, N-methyl-N-ethyl-n-decylamine, N-methyl-N-ethyl-2-propylheptylamine, N-methyl-N-ethyl-n-undecylamine, N-methyl-N-ethyl-n-dodecylamine, N-methyl-N-ethyl-n-tridecylamine, N-methyl-N-ethyl-iso-tridecylamine, N-methyl-N-ethyl-n-tetradecylamine, N-methyl-N-ethyl-n-hexadecylamine, N-methyl-N-ethyl-n-octadecylamine, N-methyl-N-ethyl-eicosyl-amine, N-methyl-N-ethyl-oleylamine;

N-methyl-N-(n-propyl)-n-heptylamine, N-methyl-N-(n-propyl)-n-octylamine, N-methyl-N-(n-propyl)-2-ethylhexylamine, N-methyl-N-(n-propyl)-n-nonylamine, N-methyl-N-(n-propyl)-iso-nonylamine, N-methyl-N-(n-propyl)-n-decylamine, N-methyl-N-(n-propyl)-2-propylheptylamine, N-methyl-N-(n-propyl)-n-undecylamine, N-methyl-N-(n-propyl)-n-dodecylamine, N-methyl-N-(n-propyl)-n-tridecylamine, N-methyl-N-(n-propyl)-iso-tri-decylamine, N-methyl-N-(n-propyl)-n-tetradecylamine, N-methyl-N-(n-propyl)-n-hexa-decylamine, N-methyl-N-(n-propyl)-n-octadecylamine, N-methyl-N-(n-propyl)-eicosyl-amine, N-methyl-N-(n-propyl)-oleylamine;

N-methyl-N-(n-butyl)-n-heptylamine, N-methyl-N-(n-butyl)-n-octylamine, N-methyl-N-(n-butyl)-2-ethylhexylamine, N-methyl-N-(n-butyl)-n-nonylamine, N-methyl-N-(n-butyl)-iso-nonylamine, N-methyl-N-(n-butyl)-n-decylamine, N-methyl-N-(n-butyl)-2-propylheptyl-amine, N-methyl-N-(n-butyl)-n-undecylamine, N-methyl-N-(n-butyl)-n-dodecylamine, N-methyl-N-(n-butyl)-n-tridecylamine, N-methyl-N-(n-butyl)-iso-tridecylamine, N-methyl-N-(n-butyl)-n-tetradecylamine, N-methyl-N-(n-butyl)-n-hexadecylamine, N-methyl-N-(n-butyl)-n-octadecylamine, N-methyl-N-(n-butyl)-eicosylamine, N-methyl-N-(n-butyl)-oleylamine;

N-methyl-N,N-di-(n-heptyl)-amine, N-methyl-N,N-di-(n-octyl)-amine, N-methyl-N,N-di-(2-ethylhexyl)-amine, N-methyl-N,N-di-(n-nonyl)-amine, N-methyl-N,N-di-(iso-nonyl)-amine, N-methyl-N,N-di-(n-decyl)-amine, N-methyl-N,N-di-(2-propylheptyl)-amine, N-methyl-N,N-di-(n-undecyl)-amine, N-methyl-N,N-di-(n-dodecyl)-amine, N-methyl-N,N-di-(n-tridecyl)-amine, N-methyl-N,N-di-(iso-tridecyl)-amine, N-methyl-N,N-di-(n-tetra-decyl)-amine;

N-ethyl-N,N-di-(n-heptyl)-amine, N-ethyl-N,N-di-(n-octyl)-amine, N-ethyl-N,N-di-(2-ethylhexyl)-amine, N-ethyl-N,N-di-(n-nonyl)-amine, N-ethyl-N,N-di-(iso-nonyl)-amine, N-ethyl-N,N-di-(n-decyl)-amine, N-ethyl-N,N-di-(2-propylheptyl)-amine, N-ethyl-N,N-di-(n-undecyl)-amine, N-ethyl-N,N-di-(n-dodecyl)-amine, N-ethyl-N,N-di-(n-tridecyl)-amine, N-ethyl-N,N-di-(iso-tridecyl)-amine, N-ethyl-N,N-di-(n-tetradecyl)-amine;

N-(n-butyl)-N,N-di-(n-heptyl)-amine, N-(n-butyl)-N,N-di-(n-octyl)-amine, N-(n-butyl)-N,N-di-(2-ethylhexyl)-amine, N-(n-butyl)-N,N-di-(n-nonyl)-amine, N-(n-butyl)-N,N-di-(iso-nonyl)-amine, N-(n-butyl)-N,N-di-(n-decyl)-amine, N-(n-butyl)-N,N-di-(2-propylheptyl)-amine, N-(n-butyl)-N,N-di-(n-undecyl)-amine, N-(n-butyl)-N,N-di-(n-dodecyl)-amine, N-(n-butyl)-N,N-di-(n-tridecyl)-amine, N-(n-butyl)-N,N-di-(iso-tridecyl)-amine;

N-methyl-N-(n-heptyl)-N-(n-dodecyl)-amine, N-methyl-N-(n-heptyl)-N-(n-octadecyl)-amine, N-methyl-N-(n-octyl)-N-(2-ethylhexyl)-amine, N-methyl-N-(2-ethylhexyl)-N-(n-dodecyl)-amine, N-methyl-N-(2-propylheptyl)-N-(n-undecyl)-amine, N-methyl-N-(n-decyl)-N-(n-dodecyl)-amine, N-methyl-N-(n-decyl)-N-(-tetradecyl)-amine, N-methyl-N-(n-decyl)-N-(n-hexadecyl)-amine, N-methyl-N-(n-decyl)-N-(n-octadecyl)-amine, N-methyl-N-(n-decyl)-N-oleylamine, N-methyl-N-(n-dodecyl)-N-(iso-tridecyl)-amine, N-methyl-N-(n-dodecyl)-N-(n-tetradecyl)-amine, N-methyl-N-(n-dodecyl)-N-(n-hexa-decyl)-amine, N-methyl-N-(n-dodecyl)-oleylamine;

Also suitable tertiary hydrocarbyl amines of formula NR¹R²R³ are monocyclic structures, wherein one of the short-chain hydrocarbyl residue forms with the nitrogen atom and with the other short-chain hydrocarbyl residue a five- or six-membered ring. Oxygen atoms and/or further nitrogen atoms may additionally be present in such five- or six-membered ring. In each case, such cyclic tertiary amines carry at the nitrogen atom or at one of the nitrogen atoms, respectively, the long-chain C₇- to C₂₀-hydrocarbyl residue. Examples for such monocyclic tertiary amines are N-(C₇- to C₂₀-hydrocarbyl)-piperidines, N-(C₇- to C₂₀-hydrocarbyl)-piperazines and N-(C₇- to C₂₀-hydrocarbyl)-morpholines.

The inventive fuel composition may comprise further customary coadditives, as described below:

Corrosion inhibitors suitable as such coadditives are, for example, succinic esters, in particular with polyols, fatty acid derivatives, for example oleic esters, oligomerized fatty acids and substituted ethanolamines.

In a preferred embodiment at least one corrosion inhibitor is added to the mixture as coadditive, very preferably a corrosion inhibitor as described in the International Patent Application with the file number PCT/EP2016/066466, filed Jul. 12, 2016, or more preferably as described in the International Patent Application with the file number PCT/EP2016/066229, filed Jul. 18, 2016, or especially as described in the International Patent Application WO 2015/114029.

Demulsifiers suitable as further coadditives are, for example, the alkali metal and alkaline earth metal salts of alkyl-substituted phenol- and naphthalenesulfonates and the alkali metal and alkaline earth metal salts of fatty acid, and also alcohol alkoxylates, e.g. alcohol ethoxylates, phenol alkoxylates, e.g. tert-butylphenol ethoxylates or tert-pentylphenol ethoxylates, fatty acid, alkylphenols, condensation products of ethylene oxide and propylene oxide, e.g. ethylene oxide-propylene oxide block copolymers, polyethyleneimines and polysiloxanes.

Dehazers suitable as further coadditives are, for example, alkoxylated phenol-formal-dehyde condensates.

Antifoams suitable as further coadditives are, for example, polyether-modified poly-siloxanes.

Antioxidants suitable as further coadditives are, for example, substituted phenols, e.g. 2,6-di-tert-butylphenol and 2,6-di-tert-butyl-3-methylphenol, and also phenylenedi-amines, e.g. N,N′-di-sec-butyl-p-phenylenediamine.

Metal deactivators suitable as further coadditives are, for example, salicylic acid derivatives, e.g. N,N′-disalicylidene-1,2-propanediamine.

Suitable solvents, especially also for fuel additive packages, are, for example, nonpolar organic solvents, especially aromatic and aliphatic hydrocarbons, for example toluene, xylenes, “white spirit” and the technical solvent mixtures of the designations Shellsol® (manufacturer: Royal Dutch/Shell Group), Exxol® (manufacturer: ExxonMobil) and Solvent Naphtha. Also useful here, especially in a blend with the nonpolar organic solvents mentioned, are polar organic solvents, in particular alcohols such as tert-butanol, isoamyl alcohol, 2-ethylhexanol and 2-propylheptanol.

When the coadditives and/or solvents mentioned are used in addition in gasoline fuel, they are used in the amounts customary therefor.

In an especially preferred embodiment, as the at least one fuel additive (D) to be used together with the mixture of complex ester and carboxylic acid mentioned which is different from the said complex ester or carboxylic acid and has detergent action is selected from (Da) polyisobutene monoamines or polyisobutene polyamines having M_(n)=300 to 5000, having predominantly vinylidene double bonds (normally at least 50 mol-% of vinylidene double bonds, especially at least 70 mol-% of vinylidene double bonds) and having been prepared by hydroformylation of the respective polyisobutene and subsequent reductive amination with ammonia, monoamines or polyamines. Such polyisobutene monoamines and polyisobutene polyamines are preferably applied in combination with at least one mineral or synthetic carrier oil, more preferably in combination with at least one polyether-based or polyetheramine-based carrier oil, most preferably in combination with at least one C₆-C₁₈-alcohol-started polyether having from about 5 to 35 C₃-C₆-alkylene oxide units, especially selected from propylene oxide, n-butylene oxide and isobutylene oxide units, as described above.

The present invention also provides an additive concentrate which comprises a mixture of at least one complex ester and at least one carboxylic acid mentioned, and at least one fuel additive which is different from the said complex esters and has detergent action. Furthermore, preferably at least one carrier oil, at least one solvent and at least one corrosion inhibitor is present. Otherwise, the inventive additive concentrate may comprise the further coadditives mentioned above. In case of additive concentrates for gasoline fuels, such additive concentrates are also called gasoline performance packages.

The at least one complex ester mentioned is present in the inventive additive concentrate preferably in an amount of 1 to 50% by weight, more preferably of 2 to 40% by weight and especially of 5 to 30% by weight, based in each case on the total weight of the concentrate.

The at least one carboxylic acid mentioned is present in the inventive additive concentrate preferably in an amount of 0.5 to 30% by weight, more preferably of 1 to 20% by weight and especially of 3 to 10% by weight, based in each case on the total weight of the concentrate.

The at least one fuel additive which is different from the complex ester and carboxylic acid mentioned and has detergent action is present in the inventive additive concentrate preferably in an amount of 20 to 91.75% by weight, more preferably of 40 to 86% by weight and especially of 60 to 76% by weight, based in each case on the total weight of the concentrate.

In a preferred embodiment the at least one fuel additive which is different from the complex ester and carboxylic acid mentioned and has detergent action is a polyisobutene amine, obtainable from a highly-reactive polyisobutene having M_(n)=300 to 5000 by hydroformylation and subsequent reductive amination with ammonia.

The at least one carrier oil is present in the inventive additive concentrate preferably in an amount of 2 to 30% by weight, more preferably of 3 to 25% by weight and especially of 5 to 20% by weight, based in each case on the total weight of the concentrate.

The at least one corrosion inhibitor mentioned is present in the inventive additive concentrate preferably in an amount of 0.25 to 10% by weight, more preferably of 0.5 to 7.5% by weight and especially of 1 to 5% by weight, based in each case on the total weight of the concentrate.

The at least one solvent mentioned is present in the inventive additive concentrate preferably in an amount of 5 to 30% by weight, more preferably of 7.5 to 25% by weight and especially of 10 to 20% by weight, based in each case on the total weight of the concentrate.

Optionally at least one dehazer may be present in amounts up to2% by weight, preferably up to 1.5% by weight, very preferably in amounts of from 0.05 to 1% by weight and especially in amounts of from 0.1 to 0.5% by weight.

In the concentrate the above-mentioned weight percentages of all components add up to 100% by weight.

The mixture of complex ester and carboxylic acid mentioned provides for quite a series of advantages and unexpected performance and handling improvements in view of the respective solutions proposed in the art. Besides reduction of the friction effective fuel saving in the operation of a spark-ignited internal combustion engine may additionally be achieved. The respective fuel additive concentrates remain homogeneously stable over a prolonged period without any phase separation and/or precipitates. The high level of intake valve and combustion chamber cleanliness achieved by the modern fuel additives is not being worsened by the presence of the complex ester mentioned in the fuel. Acceleration of internal combustion engines may further be improved. The presence of the complex ester mentioned in the fuel also provides for an improved lubricating performance of the lubricating oils in the internal combustion engine.

Additionally, the mixture according to the present invention comprising at least one complex esters and at least one monocarboxylic acid shows a lower friction compared to either the complex ester or the mono carboxylic acid alone.

The examples which follow are intended to further illustrate the present invention without restricting it.

EXAMPLES

Friction measurements of the additives formulated in Isopar® M were performed by mini-traction machine (MTM) in Stribeck mode at 60 degrees centigrade, 0.4 GPa load, and 50 percent slide to roll ratio were carried out on the complex ester (I) and the monocarboxylic acid (II), as well as on various mixtures of (I) and (II). For the measurements the mixture or single components were dissolved in Isopar® M at 1 wt %. This concentration is a model for the concentration of the components at the interphase between piston rings and cylinder wall where the friction reducing effect of the component shows the effect.

Isopar® M is a mixture of isoparaffin hydrocarbons of Exxon Mobile with a boiling range according to ASTM D86 of from 170 to 290° C.

Component 1: Complex ester obtained according to WO 2015/059063 Example 3 obtained from trimethylolpropane, adipic acid and a fatty acid mixture of coconut oil

Component 2: Oleic Acid, CAS No 112-80-1

The components were dissolved at 1 wt % in Isopar® M.

For mixed packages components 1 and 2 sum up to 1 wt % in Isopar M (Test 4-6)

Friction Friction Friction Friction Coefficient Coefficient Coefficient Coefficient Component 1 Component 2 @10 mm/s @50 mm/s @100 mm/s @500 mm/s Test 1 — — 0.183 0.175 0.169 0.133 (Isopar ® M) Test 2   1% — 0.112 0.096 0.091 0.085 Test 3 —   1% 0.111 0.091 0.083 0.073 Test 4 0.9% 0.1% 0.108 0.101 0.098 0.087 Test 5 0.7% 0.3% 0.0945 0.085 0.083 0.060 Test 6 0.5% 0.5% 0.092 0.083 0.073 0.067

The data show that the friction coefficient for the mixtures is lower than either for the complex ester or the monocarboxylic acid alone.

Additionally, the test was done in fully formulated concentrated gasoline performance packages, Effects were also measures in Isopar® M at 1 wt %.

GPP1 GPP2 GPP3 GPP5 Deposit Control Additive* 52 55 58 52 Carrier Fluid** 12 13 13 14 Corrosion Inhiitor*** 2 2 2 2 Dehazer**** 0.1 0.1 0.1 0.1 Solvent (Solvent Naphtha 16.9 11 12.9 14.9 Heavy) Component 1 17 11 10 12 Component 2 0 8 4 5 *Deposit Control Additive: amine of polyisobutene of the number average molecular weight Mn 1000 g/mol **Carrier Fluid: 15fold propoxylated, branched tridecanol ***Corrosion Inhibitor: compound according to WO 15/114029, Synthetic Example 1 ****Dehazer: commercially available, Tolad ® 286K of Baker Hughes

Composition of concentrated gasoline performance packages

Friction Friction Friction Friction Coefficient Coefficient Coefficient Coefficient @10 mm/s @50 mm/s @100 mm/s @500 mm/s Isopar ® M 0.183 0.175 0.169 0.133 GPP1 0.146 0.134 0.125 0.085 GPP2 0.138 0.128 0.121 0.075 GPP3 0.138 0.116 0.104 0.058 GPP 5 0.142 0.125 0.114 0.065

Also in fully formulated packages it can be seen that the mixture of complex esters and mono carboxylic acid results in lower friction coefficient than the complex ester alone. 

The invention claimed is:
 1. A fuel additive, comprising: (I) at least one complex ester obtained by an esterification reaction of: (A) at least one aliphatic linear or branched C₂- to C₁₂-dicarboxylic acid, (B) at least one aliphatic linear or branched polyhydroxy alcohol with 3 to 6 hydroxyl groups, and (C) a chain stopping agent comprising: (C1) at least one aliphatic linear or branched C₁- to C₃₀-mono carboxylic acid in case of an excess of the component (B), or (C2) at least one aliphatic linear or branched monobasic C₁- to C₃₀-alcohol in case of an excess of the component (A); and (II) at least one aliphatic monocarboxylic acid having from 12 to 30 carbon atoms, wherein: a weight ratio of the complex ester (I) to the aliphatic monocarboxylic acid (II) is from 20 to 80:80 to 20; and the fuel additive is adapted to function as an additive in a fuel for reducing fuel consumption in the operation of an internal combustion engine.
 2. The fuel additive of claim 1, which is adapted to function as an additive in a fuel for reducing friction in internal combustion engines.
 3. The fuel additive of claim 1, which is adapted to function as an additive in a fuel for improving acceleration of internal combustion engines.
 4. The fuel additive of claim 1, which is adapted to function as an additive in a fuel for improving the lubricity of lubricant oils contained in an internal combustion engine.
 5. The fuel additive of claim 1, wherein the component (A) is an aliphatic linear C₆- to C₁₀-dicarboxylic acid.
 6. The fuel additive of claim 1, wherein the component (B) is selected from the group consisting of glycerin, trimethylolpropane and pentaerythritol.
 7. The fuel additive of claim 1, wherein the component (C) is selected from the group consisting of (C1) an aliphatic linear or branched C₈- to C₁₈-monocarboxylic acid and (C2) a linear or branched C₈- to C₁₈-alkanol.
 8. The fuel additive of claim 1, wherein the complex ester comprises: from 2 to 9 molecule units of the component (A); and from 3 to 10 molecule units of the component (B), the component (B) being in excess compared with component (A), with remaining free hydroxyl groups of the component (B) being completely or partly capped with a corresponding number of molecule units of the component (C1).
 9. The fuel additive of claim 1, wherein the complex ester comprises: from 3 to 10 molecule units of the component (A); and from 2 to 9 molecule units of the component (B), the component (A) being in excess compared with the component (B), with remaining free carboxyl groups of the component (A) being completely or partly capped with a corresponding number of molecule units of the component (C2).
 10. The fuel additive of claim 1, wherein the at least one aliphatic monocarboxylic acid (II) is selected from the group consisting of dodecanoic acid (lauric acid), tridecanoic acid, tetradecanoic acid (myristic acid), hexadecanoic acid (palmitic acid), octadecanoic acid (stearic acid), isostearic acid, oleic acid, linoleic acid, linolaidic acid, erucic acid, arachidic acid, behenic acid, lignoceric acid and cerotic acid.
 11. A fuel composition, comprising: a gasoline fuel; and the fuel additive of claim 1, wherein the fuel composition comprises: 10 to 5000 ppm by weight of the at least one complex ester (I); 10 to 100 ppm by weight of the carboxylic acid (II); and at least one additional additive (D), which is different from the complex esters (I) and carboxylic acids (II), and comprises at least one group selected from the group consisting of: (Da) a mono- or polyamino group having up to 6 nitrogen atoms, at least one nitrogen atom having basic properties; (Db) a nitro group, optionally in combination with at least one hydroxyl group; (Dc) a hydroxyl group in combination with at least one mono- or polyamino group, at least one nitrogen atom having basic properties; (Dd) a carboxyl group or their alkali metal or alkaline earth metal salts; (De) a sulfonic acid group or their alkali metal or alkaline earth metal salts; (Df) a polyoxy-C₂-C₄-alkylene moiety terminated by at least one hydroxyl group, mono- or polyamino group, at least one nitrogen atom having basic properties, or by at least one carbamate group; (Dg) a carboxylic ester group; (Dh) a moiety derived from succinic anhydride and having at least one hydroxyl and/or amino and/or amido and/or imido group; and (Di) a moiety obtained by Mannich reaction of substituted phenols with aldehydes and mono- or polyamines.
 12. The fuel composition according to claim 11, further comprising: at least one carrier oil.
 13. The fuel composition according to claim 11, further comprising: at least one tertiary hydrocarbyl amine of formula NR¹R²R³, wherein R¹, R² and R³ are the same or different C₁- to C₂₀-hydrocarbyl residues with the proviso that the overall number of carbon atoms in formula NR¹R²R³ does not exceed
 30. 14. The fuel composition according to claim 11, wherein the group of the additional additive (D) comprises a polyisobutene monoamine or polyisobutene polyamine having M_(n)=300 to 5000 and at least 50 mol-% of vinylidene double bonds, and having been prepared by hydroformylation of the respective polyisobutene and subsequent reductive amination with ammonia, monoamines or polyamines, in combination with at least one mineral or synthetic carrier oil.
 15. An additive concentrate, comprising: the fuel additive of claim 1, and at least one fuel additive (D), which is different from the said complex esters (I) and carboxylic acids (II), and comprising a polyisobutene monoamine or polyisobutene polyamine having M_(n)=300 to 5000 and at least 50 mol-% of vinylidene double bonds, and having been prepared by hydroformylation of the respective polyisobutene and subsequent reductive amination with ammonia, monoamines or polyamines, and further comprising at least one mineral or synthetic carrier oil. 